Performance Assessment of Molecular Sieves for Sulfur Recovery Unit Tail Gas Treating

Due to stricter worldwide environmental mandates on SO2 emission from oil and gas industrial facilities, the modified Claus process, which is the primary tool for reducing emission of SO2 into the atmosphere in these facilities, has undergone a lot of innovative changes during the past decades. An example of such innovation is the addition of what is called tail gas treating (TGT) technologies. Currently, advanced TGT technologies ensure that gas plants and refineries emit less than 0.01% (v/v) of the sulfur species that enter into the sulfur recovery units; they commonly use absorption-based processes to separate sulfur species from the tail gas. Because of this requirement, TGT technologies are expensive. This paper reports the data that were obtained from bench-scale tests that were carried out to assess the feasibility of using commercially available adsorbents for the process that is described in the patent, Two-Stage Adsorption Process for Claus Tail Gas Treatment, US Patent No.10662061. In one of the embodiments of this process, the tail gas is treated in two steps. It is first dehydrated by 3A molecular sieves and then by 5A molecular sieves to remove H2S. The separation in the second step will ensure the presence of a rich H2S-laden stream that is ready for routing to the thermal reactor of the modified Claus process. The data collected in this study indicate the following: (1) Commercial molecular sieves can be used for cost-effective tail gas treatment of natural gas plants’ and refineries’ sulfur recovery units. (2) This cost-effectiveness of such use can be valid when molecular sieve material selection is as described in US Patent No.10662061, “Two-Stage Adsorption Process for Claus Tail Gas Treatment”. (3) Adsorption-based tail gas treatment is advantageous since it results in enabling the global oil and gas industry to virtually eliminate all SO2 emissions from its facilities.